1. Field of the Invention
The present invention relates to a honeycomb filter and an exhaust gas purifying apparatus.
2. Discussion of the Background
Since emphasis has been put on environmental problems in recent years, auto industry requires environmentally-friendly engines with good fuel economy.
Diesel engines are advantageously superior in fuel economy to gasoline engines, but unfortunately generate particulate matters (hereinafter, also referred to as PMs) such as soot. Therefore, it is necessary to purify the PMs in exhaust gases by providing an exhaust gas purifying apparatus.
The gasoline engines advantageously have less emission of PMs compared with the diesel engines. Therefore, in general, it is presumably not necessary to provide an exhaust gas purifying apparatus for purifying the PMs. However, disadvantageously, the gasoline engines are inferior in fuel economy to the diesel engines.
Since automobile buyers tend to make much of fuel economy of automobiles in recent years, the number of automobiles equipped with a gasoline direct injection engine (GDI) excellent in fuel economy among the gasoline engines is expected to increase. However, since exhaust gases emitted from the gasoline direct injection engine contain PMs in a small amount, it seems necessary to install an exhaust gas purifying apparatus and purify PMs in the exhaust gas.
The exhaust gas purifying apparatus used for purifying an exhaust gas emitted from a diesel engine is manufactured by installing, in a metal casing, a honeycomb filter made of materials such as ceramics. The exhaust gas purifying apparatus can purify the exhaust gas by introducing the exhaust gas thereinto from the gas inlet side thereof, allowing the exhaust gas to pass through the filter, and discharging the exhaust gas from the gas outlet side thereof.
In such a filter, a plurality of cells are longitudinally disposed in parallel with one another with a cell wall interposed therebetween. The plurality of cells are all sealed at either one end, and therefore, an exhaust gas that flows into one cell never fails to pass through the cell wall that separates the cells, and then is discharged from another cell. Specifically, according to an exhaust gas purifying apparatus including such a filter, PMs contained in the exhaust gas are captured by the cell wall when passing through the filter, and as a result, the exhaust gas is purified.
Japanese Patent Application Publication (KOKAI) 2001-96113 discloses a honeycomb filter having such a structure and an exhaust gas purifying apparatus including a honeycomb filter installed in a casing.
The contents of Japanese Patent Application Publication (KOKAI) 2001-96113 are incorporated herein by reference in their entirety.